1. Field of the Invention
The present invention relates to weighing machines that start weighing an object automatically.
2. Related Art
A known weighing machine starts weighing an object when it senses that the object is placed on its weighing platform. A weighing machine disclosed in U.S. Pat. No. 4,326,596, for example, starts weighing when it senses that a mechanical switch disposed under the weighing platform is turned on. This type of weighing machine saves the user from operating a power switch of the weighing machine and is convenient for use.
The mechanical switch, however, has a high possibility of becoming defective because of wear or the like through the repetition of the on-off operation, and could decrease the durability of the weighing machine. Another problem is that a built-in mechanical switch could increase the thickness of the weighing machine, degrading the stability. In addition, lower-power weighing machines with improved weighing precision are needed.